Mediation of pinocytosis in cultured arterial smooth muscle and endothelial cells by platelet-derived growth factor

Pinocytosis was measured in monkey aortic smooth muscle cells (SMC), bovine aortic endothelial cells, and Swiss 3T3 cells in culture as cellular uptake of [U-(14)C]sucrose and horseradish peroxidase (HRP) from the tissue culture medium. Monkey arterial SMC and Swiss 3T3 cells were maintained in a quiescent state of growth at low cells density in medium containing 5 percent monkey plasma-derived serum (PDS). Replacement of PDS with 5 percent monkey whole blood serum (WBS) from the same donor, or addition to PDS of partially purified platelet-derived growth factor(s) (PF), resulted in a marked stimulation of pinocytosis as well as of cellular proliferation. In SMC, enhancement of the rate of pinocytosis occurred 4-6 h after exposure to WBS or PF, and the rate was up to twofold higher than the rate in medium containing PDS. In contrast, [(3)H]thymidine uptake by SMC did not increase until 12-16 h after exposure to PF. In endothelial cells the presence of PF or WBS did not enhance either the rate of pinocytosis or the rate of proliferation over that in PDS. Thus, endothelial cells did not become quiescent at subconfluent densities in PDS but maintained rates of proliferation and pinocytosis that were equivalent to those in WBS. By autoradiography, the fraction of labeled nuclei in SMC cultures 24 h after change of medium increased from 0.061 +/- 0.004 in quiescent cultures to 0.313 +/- 0.028 after exposure to WBS or PF. In contrast, labeling indices of endothelial cells were similar for cultures grown in PDS, WBS, or PF at any single time point after change of medium. These findings suggest that the rate of pinocytosis maybe be coupled in some fashion to growth regulation, which may be mediated in part by specific growth factors, such as that derived from the thrombocyte.     

Artificial neural network learning of nonstationary behavior in time series

We refine and complement a previously-proposed artificial neural network method for learning hidden signals forcing nonstationary behavior in time series. The method adds an extra input unit to the network and feeds it with the proposed profile for the unknown perturbing signal. The correct time evolution of this new input parameter is learned simultaneously with the intrinsic stationary dynamics underlying the series, which is accomplished by minimizing a suitably-defined error function for the training process. We incorporate here the use of validation data, held out from the training set, to accurately determine the optimal value of a hyperparameter required by the method. Furthermore, we evaluate this algorithm in a controlled situation and show that it outperforms other existing methods in the literature. Finally, we discuss a preliminary application to the real-world sunspot time series and link the obtained hidden perturbing signal to the secular evolution of the solar magnetic field.     

Facet shapes and thermo-stabilities of H<Subscript>2</Subscript>SO<Subscript>4</Subscript>•HNO<Subscript>3</Subscript> hydrates involved in polar stratospheric clouds

The nucleation, ice crystal shapes and thermodynamic stability of polar stratospheric clouds particles are interesting concerns owing to their implication in the ozone layer destruction. Some of these particles are formed by conformers of H₂O, HNO₃, and H₂SO₄. We carried out calculations using density functional theory (DFT) to obtain optimized structures. Several stable trimers are achieved —divided in two groups, one with HNO₃ moiety, second with H₂SO₄ moiety— after pre-optimization at B3LYP/6-31G and subsequently optimization at B3LYP/aug-cc-pVTZ level of theory. For both most stable conformers five H₂O molecules are added to their optimized trimers to calculate hydrated geometries. The OH stretching harmonic frequencies are provided for all aggregates. The zero-point energy correction (ZEPC), relative electronic energies (?E), relative reaction Gibbs free energies ?(?G)_k-relative, and cooling constant (K _cooling ) are reported at three temperatures: 188 K, 195 K, and 210 K. Shapes given in our calculations are compared with various experimental shapes as well as comparisons with their thermo-stabilities.

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Graphical Abstract Facet shapes and thermo-stabilities of H₂SO₄?HNO₃ hydrates involved in polar stratospheric clouds. IR spectrum of WNS-1+5W structure and its circular facet

     

Control of stem cell fate by engineering their micro and nanoenvironment

Stem cells are capable of long-term self-renewal and differentiation into specialised cell types, making them an ideal candidate for a cell source for regenerative medicine. The control of stem cell fate has become a major area of interest in the field of regenerative medicine and therapeutic intervention. Conventional methods of chemically inducing stem cells into specific lineages is being challenged by the advances in biomaterial technology, with evidence highlighting that material properties are capable of driving stem cell fate. Materials are being designed to mimic the clues stem cells receive in their in vivo stem cell niche including topographical and chemical instructions. Nanotopographical clues that mimic the extracellular matrix(ECM) in vivo have shown to regulate stem cell differentiation. The delivery of ECM components on biomaterials in the form of short peptides sequences has also proved successful in directing stem cell lineage. Growth factors responsible for controlling stem cell fate in vivo have also been delivered via biomaterials to provide clues to determine stem cell differentiation. An alternative approach to guide stem cells fate is to provide genetic clues including delivering DNA plasmids and small interfering RNAs via scaffolds. This review, aims to provide an overview of the topographical, chemical and molecular clues that biomaterials can provide to guide stem cell fate. The promising features and challenges of such approaches will be highlighted, to provide directions for future advancements in this exciting area of stem cell translation for regenerative medicine.     

Confocal reader for biochip screening and fluorescence microscopy

We developed a fluorescence reader for the sensitive detection of surface-generated fluorescence. The system is applicable for high resolution imaging as well as for the readout of large biochips. The surface of a microscope coverslip is scanned with a laser beam focused to a waist diameter of 500 nm (FWHM) by means of a single aspheric lens. Scanning large areas with a focused beam usually evokes the need of automatic control elements to adjust the laser spot to the designated position at the surface. Due to the special design of the reader, the focus keeps at the plane of the surface even when scanning large areas, obviating the requirement of any real time control. Thus the instrument is straightforward and inexpensive. Nevertheless it features a high sensitivity and high optical resolution. The versatility of the instrument is demonstrated by imaging cells and reading out a DNA-chip. The excellent sensitivity is shown by detecting single fluorescently labeled antibodies.     

Genetic covariance between indices of body condition and immunocompetence in a passerine bird

Background  

Condition-dependence is a ubiquitous feature of animal life histories and has important implications for both natural and sexual selection. Mate choice, for instance, is typically based on condition-dependent signals. Theory predicts that one reason why condition-dependent signals may be special is that they allow females to scan for genes that confer high parasite resistance. Such explanations require a genetic link between immunocompetence and body condition, but existing evidence is limited to phenotypic associations. It remains unknown, therefore, whether females selecting males with good body condition simply obtain a healthy mate, or if they acquire genes for their offspring that confer high immunocompetence.     

Nature’s Palette: Characterization of Shared Pigments in Colorful Avian and Mollusk Shells

Pigment-based coloration is a common trait found in a variety of organisms across the tree of life. For example, calcareous avian eggs are natural structures that vary greatly in color, yet just a handful of tetrapyrrole pigment compounds are responsible for generating this myriad of colors. To fully understand the diversity and constraints shaping nature’s palette, it is imperative to characterize the similarities and differences in the types of compounds involved in color production across diverse lineages. Pigment composition was investigated in eggshells of eleven paleognath bird taxa, covering several extinct and extant lineages, and shells of four extant species of mollusks. Birds and mollusks are two distantly related, calcareous shell-building groups, thus characterization of pigments in their calcareous structures would provide insights to whether similar compounds are found in different phyla (Chordata and Mollusca). An ethylenediaminetetraacetic acid (EDTA) extraction protocol was used to analyze the presence and concentration of biliverdin and protoporphyrin, two known and ubiquitous tetrapyrrole avian eggshell pigments, in all avian and molluscan samples. Biliverdin was solely detected in birds, including the colorful eggshells of four tinamou species. In contrast, protoporphyrin was detected in both the eggshells of several avian species and in the shells of all mollusks. These findings support previous hypotheses about the ubiquitous deposition of tetrapyrroles in the eggshells of various bird lineages and provide evidence for its presence also across distantly related animal taxa.